Fresnel zone

About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.

3D‐Printed Holographic Fresnel Lenses

Abstract: Additive manufacturing processes are capable of fabricating optical devices, including the production of contact lenses, waveguides, and Fresnel lenses used in a variety of applications. This study presents a novel fabrication method for high‐quality Fresnel lenses through a vat photopolymerization 3D printing method. Here, the 3D printing process is integrated with the micro/nanostructure fabrication to produce 3D optical components with imprinted micro/nanostructures in a single step. This straightforward approach allows imprinting a micro‐pattern (5 μm features size) onto the flat surface of a 3D‐printed Fresnel lens, achieve light focusing properties along with holographic rainbow effects. The printed lenses achieve focal lengths within ≤8 mm deviation from the predicted values. Such holographic Fresnel lenses are highly desirable in imaging‐based miniature spectrometers for mechanoluminescence sensoring. Thus, the masked stereolithography (MSLA) based 3D printing process can produce normal and holographic Fresnel lenses, vital in optical sensing and communication.

Time Lapse Seismic Data Selection for Acquisition and Processing by Fresnel Zone Estimation

Abstract: P667 TIME LAPSE SEISMIC DATA SELECTION FOR ACQUISITION AND PROCESSING BY FRESNEL ZONE ESTIMATION P.L.A. WINTHAEGEN 1 J.F.B. BOLTE 2 and D.J. VERSCHUUR 2 Summary 1 For selecting data to image a specific part of the subsurface a methodology for determining the Fresnel zone at the surface (zone of influence) is proposed. This methodology is based on the Common Focal Point matrix and is fully data-driven by using 2D or 3D seismic data. By applying this method not only the contributing traces for processing are selected but also the source and receiver positions needed for acquisition. The presented methodology can

Mathematical Model and Algorithm for Determination of Minimum Antenna Mast Height for Terrestrial Line of Sight Microwave Link with Zero Path Inclination

Abstract: In this paper, mathematical model and algorithm for determination of minimum antenna mast height for terrestrial line of sight microwave link with zero path inclination is presented. The mathematical expressions developed are used for computing relevant link parameters while the algorithm gives the procedure for using the mathematical expressions for computing the minimum antenna mast heights. Sample 40km 10GHz Ku-band microwave link is used to demonstrate the application of the model and algorithm; in this case, the transmitter is located at longitude 7.711747 and latitude 5.178536 and the receiver is located at longitude 8.039903and latitude 5.055223. The link is required to make a minimum of 100% clearance with respect to the Fresnel zone 1. The results show that the transmitter and receiver antenna are at the same line of sight height of 158.7 m whereas the transmitter antenna mast height is 68.8 m while the receiver antenna mast height is 109.7m. Also, the maximum obstruction height of 128.58m occurred at a distance of 14306.98m from the transmitter with percentage clearance of 100% in respect of Fresnel zone 1. The result shows that the model can be used to ensure that the specified percentage clearance is achieved through the application of the models presented in this paper.

Evaluation of plenoptic algorithm performance for measuring scene spectra captured by a diffractive plenoptic camera

Abstract: A diffractive plenoptic camera is a novel approach to the traditional plenoptic camera which replaces the main optic with a Fresnel zone plate making the camera sensitive to wavelength instead of range. Algorithms are necessary, however, to reconstruct the image produced by these plenoptic cameras. This paper provides the first quantification of the effectiveness of four different types of post-processing algorithms on a simulated Fresnel zone light field spectral imaging system. The four post-processing algorithms used were standard digital refocusing, 3D deconvolution through a Richardson-Lucy algorithm, a novel Gaussian smoothing algorithm, and a custom-made super resolution algorithm. For the digital refocusing algorithm, the image quality decreased as the wavelength difference from design increased. In comparison, in the Richardson Lucy deconvolution algorithm, the image returned to the same quality as at the design wavelength if enough iterations were used and generally provided results on par with the best near the design wavelength of the Fresnel zone plate and by far the best results far from design at the cost of extensive computation time. The super resolution method, in general, performed better than the standard digital refocusing while the Gaussian smoothing algorithm performed on par with digital refocusing. As a consequence, if time is not a factor, deconvolution should be used in general, while the super resolution method provides faster results if time is an issue. Still, each algorithm outperformed the others in specific cases which allows the best results to be obtained by choosing the algorithm that meets operational requirements and limitations.

Metallic zone plates for sectoral horns

Abstract: Fresnel zone plates are planar devices with lens-like focusing properties. The planar structure makes a zone plate easy to construct and provides lower absorption loss and weight. This paper reports on the Fresnel zone plates to be constructed from metal. Typically in the past, zone plates have been fabricated from dielectric material. In addition to the advantages mentioned earlier, metallic zone plates can be machined or cast directly into sectoral horns.